1. Field of the Invention
The present invention relates to a new and improved flame retaining nozzle tip for a burner in a pulverized fuel fired furnace. More particularly the present invention relates to a flame retaining nozzle tip designed to be used for burner retrofit applications in both wall fired furnaces as well as tangentially fired furnaces. The new and improved nozzle tip provides improved flame retention and stability without premature burn up and provides better turn down characteristics allowing low load operation with little or no support fuel being required. More specifically a new and improved flame retaining nozzle tip of the present invention is especially well adapted for use in burner retrofit applications and provides much improved loss on ignition characteristics (LOI) and high efficiency operation for a retrofitted coal burner over a wide range of loads.
2. Background of the Prior Art
U.S. Pat. No. 4,348,170 discloses a dual register, split-stream, burner assembly with a flow dividing cone.
U.S. Pat. No. 4,356,975 discloses a nozzle tip for a pulverized coal burner having splitter vanes provided with abrasion-resistant and heat-resistant material.
U.S. Pat. No. 4,520,739 discloses a nozzle tip for a pulverized coal burner employing three interconnected components including a temperature-resistant end cap, a base or body and a replaceable abrasion-resistant insert between the body and the end cap.
U.S. Pat. No. 5,257,927 discloses a low NO.sub.x burner employing a plurality of gas nozzles which individually inspirate a portion of the combustion air and the burner includes a spin vane diffuser to rotate and mix the gases within the primary combustion zone.
U.S. Pat. Nos. 4,479,442 and 4,457,241 owned by the assignee of the present application and incorporated herein by reference, disclose a high efficiency pulverized fuel burner for furnaces receiving a flowing stream of pulverized coal and primary air. The burner includes a Venturi mounted adjacent an outlet end of a coal nozzle and has a conical flow spreader and swirl vanes. The spreader cone is mounted in an outlet end divergent flow section of the Venturi structure and form an annular expanding flow pattern of the coal and primary air mixture as it is discharged into the combustion zone of a furnace. These burners have been found to greatly improve NO.sub.x reduction characteristics and the new and improved flame retaining nozzle tip in accordance with the present invention can be utilized in combination with the low NO.sub.x Venturi burner of U.S. Pat. Nos. 4,479,442 and 4,457,241 to further improve the operating characteristics.